Christianity in the 5th century in the context of "Christianity in the 4th century"

The Church Fathers, Early Church Fathers, Christian Fathers, or Fathers of the Church were ancient and influential Christian theologians and writers who established the intellectual and doctrinal foundations of Christianity. The historical period in which they worked became known as the Patristic Era and spans approximately from the late 1st to mid-8th centuries, flourishing in particular during the 4th and 5th centuries, when Christianity was in the process of establishing itself as the state church of the Roman Empire.

For many denominations of Christianity, the writings of the Ante-Nicene Fathers, Nicene Fathers and Post-Nicene Fathers are included in Sacred Tradition. As such, in traditional dogmatic theology, authors considered Church Fathers are treated as authoritative for the establishment of doctrine. The academic field of patristics, the study of the Church Fathers, has extended the scope of the term, and there is no definitive list. Some, such as Origen and Tertullian, made major contributions to the development of later Christian theology, but certain elements of their teaching were later condemned.

Patriarchate (/ˈpeɪtriɑːrkɪt, -keɪt/, UK also /ˈpætri-/; Ancient Greek: πατριαρχεῖον, patriarcheîon) is an ecclesiological term in Christianity, referring to the office and jurisdiction of a patriarch.

According to Christian tradition, three patriarchates—Rome, Antioch, and Alexandria—were established by the apostles as apostolic sees in the 1st century. These were officially recognized by the First Council of Nicaea. The Patriarchate of Constantinople was added in the 4th century, and the Patriarchate of Jerusalem followed in the 5th century. These five sees were later recognized collectively as the pentarchy by the Council of Chalcedon in 451.

The Church of the East (Classical Syriac: ܥܕܬܐ ܕܡܕܢܚܐ ʿĒḏtā d-Maḏenḥā) or the East Syriac Church, also called the Church of Seleucia-Ctesiphon, the Persian Church, the Assyrian Church, the Babylonian Church, the Chaldean Church or the Nestorian Church, is one of three major branches of Eastern Nicene Christianity that arose from the Christological controversies in the 5th century and the 6th century, alongside that of Miaphysitism (which came to be known as the Oriental Orthodox Churches) and Chalcedonian Christianity (from which Catholicism, Eastern Orthodoxy and Protestantism would arise).

Having its origins in Mesopotamia during the time of the Parthian Empire, the Church of the East developed its own unique form of Christian theology and liturgy. During the early modern period, a series of schisms gave rise to rival patriarchates, sometimes two, sometimes three. In the latter half of the 20th century, the traditionalist patriarchate of the church underwent a split into two rival patriarchates, namely the Assyrian Church of the East and the Ancient Church of the East, which continue to follow the traditional theology and liturgy of the mother church. The Chaldean Catholic Church based in Iraq and the Syro-Malabar Church in India are two Eastern Catholic churches which also claim the heritage of the Church of the East.